A switch-mode power converter produces an output voltage by switching reactive elements into different topologies using a switching network. In those cases in which the reactive elements are capacitors, the resulting power converter is referred to as a switched-capacitor power converter. In a typical switched-capacitor converter, the number of capacitors and switches increases as the conversion gain increases.
The switches in such converters must be driven to open and close at opportune times. In those cases in which the switch is implemented as a MOSFET, driving a switch requires causing charge to flow into a gate terminal so as to cause an electric field. In an enhancement mode MOSFET, this electric field causes an inversion layer that permits charge to flow between source and drain.
A circuit that causes charge to flow into a transistor's gate terminal is often called a “gate driver.” The charge that enters the gate driver obviously has to come from somewhere. For this reason, a gate driver requires a power supply.
As used herein, conversion gain represents a voltage gain if the switched capacitor power converter produces an output voltage that is larger than the input voltage or a current gain if the switched capacitor power converter produces an output voltage that is smaller than the input voltage.